Authors:

We have developed a model to calculate the average charge on a
Cooper pair
box in the presence of quasiparticle poisoning. The model uses a
master
equation approach to find the probabilities for the box to be in
the even or
odd state. The transition rates between the two states are
calculated
assuming a fixed number of non-equilibrium quasiparticles in the
leads and
island of the box. We fabricated Al/AlOx/Al devices with a Cooper
pair box
capacitively coupled to an SET and measured the charge on the box
for SET
bias currents ranging from about 1 pA to 1 nA. We find good
agreement
between the theory and measurements in the temperature range from
60 mK to
300 mK. For large SET bias the poisoning in the Cooper pair box
increases
and the charge staircase develops additional features. Our model
is capable
of qualitatively reproducing the features induced by the
measuring SET.

*This work was supported by the National Security Agency

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2006.MAR.W39.13